FeS₂

This sample of marcasite is displayed in the Smithsonian Museum of Natural History. Marcasite is a sulfide mineral of iron with the composition FeS₂. The sample at left is about 15 cm across and is from Northern Indiana stone quarry, Indiana.

This sample of marcasite is about 15 cm across and is from Picher, Oklahoma.

This sample of marcasite is about 14 cm across and is from Montreal, Wisconsin.